Synthesis, structure and property studies of a new series of rare earth (Ce, Tb) bismuth silicates

A new series of rare earth bismuth silicates has been synthesized by flux method and solid state reaction . LnBiSiO 5 (Ln ​= ​Ce, Tb) crystallizes in a triclinic space group P -1 with cell parameters a  ​= ​5.6763(2) Å, α  ​= ​105.591(3)° b  ​= ​6.7922(3) Å, β  ​= ​110.551(3)° c  ​= ​6.9593(2) Å, γ  ​= ​99.733(3)°, Z ​= ​2. They exhibit a novel three-dimensional structure consisting of zig-zag chains of edge-sharing Ce/TbO 8 polyhedra that are further linked by SiO 4 units and Bi 2 O 8 clusters. The optical band gap (E g ) of TbBiSiO 5 was estimated to be 3.84 ​eV from UV–Vis-IR diffuse reflectance spectra. Photoluminescence measurements suggest that due to the cooperative interaction of Bi and Tb the excitation bands monitored at 544 ​nm are shifted towards longer wavelength which may favor commercial UV diode excitation. The magnetic measurements show that TbBiSiO 5 exhibits paramagnetic behavior without magnetic transitions down to 1.8 ​K.